The Civil Aviation Authority of Thailand (CAAT) is planning to extend its inbound flight ban for another 15 days to prevent a possible increase of Covid-19 infections as over 1,000 Thais are scheduled to return to the country this week.

If the ongoing ban, which will end on April 30, is extended, it will be the fourth in a series of temporary aviation closures which began on April 4.

Officials usually assess the situation every 15 days and "we may need to further disallow passenger aircraft from entering Thailand, but a final say will be given by the Public Health Ministry," CAAT chief Chula Sukmanop said on Monday.

Daily reports of new Covid-19 cases in the country have been below 20 since April 21, except on Saturday when the numbers rose to 53 due to infections recorded among a group of detained illegal migrant workers.

However, Mr Chula said, authorities cannot be complacent as infection rates overseas, including in neighbouring countries, remain high, making the situation volatile.

Early this month, the CAAT has extended its aviation closure to April 18 after the first ban ended on April 6.

It then extended the ban from April 18 to this Thursday.

A total of 1,078 Thais have registered to return this week, officials said. Most of them (601) will come from India, followed by 207 from Australia, 168 from New Zealand, 42 from Spain, 35 from Japan and 25 from the Netherlands.

All passengers, including about 50 children, are required to go through strict health checks and be kept under isolation for 14 days.

The Centre for Covid-19 Situation Administration (CCSA) has reported that about 9,000 Thais who have registered with Thai embassies and consulates in overseas countries will return to Thailand after April 30.

Health officials are taking a close look at all returnees, particularly workers from Malaysia, as they are eager to maintain the low infection rates recorded in the second half of April.